Hi Ali
How could I resist a challenge like that?
Forget, for the moment, everything you know about credit cards and interest free periods and minimum payments. They are irrlevant.
The interest is calculated from the day of purchase to the day you paid off the purchase.
So you "borrowed" 2425 and paid off €75.
You will be charged interest on the €2425.
You borrowed €100 on 1 September
You received a statement on 25 sept with this item on it
You did not pay this off, so you were charged interest on it on the next statement on 25 October.
So that would be nearly two months interest.
So you averaged 1.5 months' interest on 2425 @ 1% = around €36.
So it looks about right.
If you pay the full amount by the payment date, they waive this interest. if you don't pay the full amount or if you mist the payment date, then they charge the interest as set out above.
Brendan